1. Field of the Invention
The present invention relates to symbol recognition, more particularly, it relates to symbol recognition using multidimensional preprocessing at multiple resolutions.
2. Description of the Prior Art
Character recognition systems suffer from two problems. In an effort to limit the number of cells in an array that describes a character, a quantization error is introduced, and even with a limited number of cells, a large amount of computational time is still required to identify the character.
Some character recognition systems use a pixel array to describe a character. For example, U.S. Pat. No. 5,067,164 describes a system that uses a pixel array. Since a character comprises many pixels, a pixel array produces a large number of cells. This problem is compounded when an array with several dimensions is used to include additional information describing the character. As a result, it is necessary to map several pixels into a single cell of the array, where each cell encompasses a given volume. This reduces the number of cells and thereby reduces the number of computations required to compare the pixel array with a reference array. Unfortunately, by mapping several pixels into a cell, a quantization error is introduced. This can result in a character recognition system that has unacceptable error rates.
Other character recognition systems represent a character using a feature vector or feature array that describes the character. In order to provide a description with sufficient information, many cells are included in the array. The feature array is then compared against a set of reference feature arrays to determine the identity of the character in question. This technique requires a comparison between a feature array with many cells, and a large selection of reference arrays, where each reference array has many cells. This comparison requires a large amount of computational time, and is therefore unacceptable in many applications.